Oat based cereal products for human consumption primarily include grain flakes and oat flour although other specialty oat based or oat derived products are also known. Grain flakes of various sizes are used for oatmeal, granola products, and as topical additives for various products, especially for breads. The processing of oat groats for forming into oat flakes is substantially different than for the preparation of a whole grain oat flour.
In prior oat flour production, dehulled oats or oat groats are steamed for enzyme inactivation and then milled to form a shelf stable whole grain oat flour. The oat flour can be subsequently processed to form cooked cereal doughs which in turn are fabricated into R-T-E cereals of various types including flakes, biscuits, and importantly, puffed R-T-E cereals. The puffed R-T-E cereals can be of the popular ring shape or fabricated into other shapes, such as alphabet letters or animal shapes. By "whole grain oat flour" is meant herein an oat flour including its oil component obtained from dehulled oat groats.
Processing for the provision of puffed whole grain oat based R-T-E cereals from cooked cereal doughs is particularly complex due to the multiplicity of problems of providing a whole grain R-T-E cereal in general, a puffed whole grain R-T-E cereal, and/or an oat based R-T-E cereal in particular, whether flaked or puffed. For example, one particular problem is that whole grain oat based cooked cereal doughs are notoriously difficult to puff possibly due to the high levels of fat and soluble gums, e.g., beta glucan. A second particular problem is that whole grain oat based R-T-E cereal products experience particularly severe stability problems due to the fat content. For these reasons, some puffed oat based R-T-E cereal products are prepared from defatted oat flour or are merely whole oat flour containing (i.e., have high levels of added starch or other cereal materials). Because of the difficulties of producing a puffed whole oat piece from cooked cereal dough pellets, gun puffing is used since gun puffing is the most vigorous form of cereal pellet puffing.
A general problem in providing a puffed R-T-E cereal resides in the provision of an R-T-E cereal having the desirable "cooked grain" flavor. Many cereals can be cooked to gelatinize the starch component in a relatively short period of time. However, the imparting to the cooked cereal dough of a "nutty" or cooked grain flavor requires extended cook times. Traditional batch or semi-continuous cereal cookers can provide the requisite lengthy residence or long cook times to develop the desired "cooked grain" flavor feature.
Unfortunately, however, traditional cookers used in the manufacture of whole grain based puffed R-T-E cereal products are very expensive. Thus, it would be highly desirable to be able to either increase the output of such cereal cookers by reducing the required cook time needed to produce a desired level of cooked cereal flavor or to increase the desirable cooked flavor for a given cook time in such traditional long cook time cereal cookers.
Moreover, cooker extruders, whether single screw or double screw are increasingly popular, especially in the production of directly expanded R-T-E cereal products. However, since the residence time in the cooker extruder is so short, (e.g., 0.5 to eight minutes) the cooked cereal dough produced often is characterized as having an "uncooked" or "green" flavor rather than the desirable "cooked" or "nutty" flavor. Adding flavor additives to rectify the flavor deficiency is both expensive and marginally effective. Of course, the residence time in the cooker extruder can be increased modestly to further develop desirable flavor. However, the increase in the residence time in the cooker extruder also increases the amount of work imparted to the cooked cereal dough. As the cooked cereal dough is worked more, the texture is adversely affected leading to a pasty finished product having an undesirable eating texture.
In direct expansion, the finished puffed products are produced directly from the cooker extruder thereby eliminating such conventional intermediate steps as dough tempering, pellet forming, pellet drying, and gun puffing of the pellets. By avoiding these intermediate steps, the cost of producing the finished R-T-E cereal is dramatically reduced.
Due to the difficulty in developing cooked grain flavors in whole oat based R-T-E cereal doughs, cooker extruders have not been used for the preparation of direct expanded puffed whole grain oat R-T-E cereals.
Surprisingly, in the present invention it has been found that by extending the steaming step and by adding a particular selected heat treatment of the oat groats prior to milling into a flour, that an improved high flavor, and partially cooked oat flour product can be prepared. Utilization of this high flavor, partially cooked oat flour can be used in conventional cereal processing with shorter cook times to produce finished R-T-E puffed whole grain oat cereal products having a desirable "nutty" cooked cereal flavor. By utilization of such an improved oat flour, increases in cereal processing outputs of up to 10% or more can be obtained without a loss in desirable end product flavor quality.
More surprisingly, the improved whole grain oat flour can also be used in short cook time cooker extruders to produce whole oat grain based puffed R-T-E cereals of desirable texture and flavor properties. Even more surprisingly, directly expanded puffed whole grain oat based R-T-E cereals can be prepared which nonetheless exhibit high levels of cooked grain flavor.